英语脑筋急转弯：两个父亲和两个儿子在一辆车里，但车里只有三个人

Question
问题

Two fathers and two sons are in a car, yet only three people are in the car. How?
两个父亲和两个儿子在一辆车里，但车里只有三个人。这是怎么回事？

Answer
答案

They are grandfather, father and son.
他们是祖父、父亲和儿子。